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1991 Mitsubishi 3000GT only running on 4 cylinders

Tiny
TORTUGADEMUERTO
  • MEMBER
  • 1991 MITSUBISHI 3000GT
  • 3.0L
  • V6
  • FWD
  • MANUAL
  • 120,000 MILES
OK, I have do a little bit of research already, but I know that it can be dangerous if I don't know what I am doing. Basically, two of my cylinders aren't firing. I checked the coil pack (by switching it with another working one in the car) but the new one didn't spark either. I got out my trusty wire tester and saw that there was con constant stream of power going into and leaving the coil pack, but it wasn't fluttering (the power for the other coil packs 'flutter' in time with the spark.) So, I also checked the ECM (under the center console behind stereo) and it looked like a couple of the capacitors possibly could have leaked, either that, or the board is just a little rusty (the car did sit for 6 years with a slipped timing belt before I got it). The car does run and drive, but not very well. I would really feel much safer if the car ran on all 6 instead of just 4 cylinders. My thought is to just replace the ECM, but I don't want to spend that much money just to find out that the problem was something else. Other than those 2 cylinders not getting spark, the car is basically fine. What suggestions could you offer?
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Tuesday, April 15th, 2014 AT 5:52 PM

13 Replies

Tiny
RASMATAZ
  • MECHANIC
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You didn't mentioned what cylinders
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Tuesday, April 15th, 2014 AT 7:30 PM
Tiny
TORTUGADEMUERTO
  • MEMBER
  • 7 POSTS
2 and 5 I think. It is the 2 middle ones.
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Tuesday, April 15th, 2014 AT 7:36 PM
Tiny
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Check the power transistor for 2/5 cylinders
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Tuesday, April 15th, 2014 AT 9:43 PM
Tiny
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  • MEMBER
  • 7 POSTS
I pulled the power transistor out and checked each position (used 1.5V battery + volt meter). It seemed that one of the nodes didn't offer any resistance when checked (measured around 44 with or without the battery connected), while the other 2 nodes had a little bit of resistance once the battery was hooked up (dropped from 44 to around 32). I had my meter set at 200k Ohms because it seemed to be the only Ohm setting that was taking any measurements. What are your thoughts now?
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Wednesday, April 16th, 2014 AT 12:52 PM
Tiny
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Test 2/5 coils primary and secondary windings resistances-
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Wednesday, April 16th, 2014 AT 5:41 PM
Tiny
TORTUGADEMUERTO
  • MEMBER
  • 7 POSTS
Would that be in reference to the coil pack? Or the ignition coil? Either way, I replaced the ignition coil with a new one, no fix. I also know that the coil pack isn't the problem because I switched it out with a different one that is running perfectly, and still the same problem. The one that was originally "not working" is now working strong and giving spark to 3 & 6. Anything that I find online about "primary and secondary winding resistance" has to do with the coil pack. Is this in reference to something else? Can you please give detail? Thank you for your help.
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Thursday, April 17th, 2014 AT 11:47 AM
Tiny
TORTUGADEMUERTO
  • MEMBER
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One more question. I was told that the heavy metal part of the coil pack is basically a big capacitor. This is the part that bolts straight to the block. Could this part some how be grounding (or not grounding if it is supposed to)?
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Thursday, April 17th, 2014 AT 11:53 AM
Tiny
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2/5 cyl shares the same coil-could be the coil itself-Dunno about the big capacitor if it is or not-sorry
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Thursday, April 17th, 2014 AT 12:05 PM
Tiny
TORTUGADEMUERTO
  • MEMBER
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OK, so I switched out the coil again. The problem still persists with the same cylinders (2 & 5) with the different coil. Like I said before, the coil for 2 & 5 isn't getting the same stream of power as the other coils. I checked the PTU and it is just fine. Not sure where to go from here.
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Thursday, April 17th, 2014 AT 1:02 PM
Tiny
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Last resort computer-It might not be firing the coil for 2/5 or the crankshaft position sensor
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Thursday, April 17th, 2014 AT 3:45 PM
Tiny
TORTUGADEMUERTO
  • MEMBER
  • 7 POSTS
Just so you know, I found out that the problem is not my ECU. My ECU is good, but one of the wires going from the ECU to my PTU is grounding out somewhere. My only problem is finding exactly where the grounding is. Just thought I would share just in case you run into a problem similar to mine.
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Thursday, April 24th, 2014 AT 3:38 PM
Tiny
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Thank You for sharing-Good Luck
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Thursday, April 24th, 2014 AT 4:49 PM
Tiny
DENMARK1
  • MEMBER
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Hi, TortugaDeMuerto

Can See it is an old post, but did you figured out of what was wrong with the car, hav the same error on our 3000GT VR4 91, and have tried everything, except changing the ECU.
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Tuesday, May 5th, 2015 AT 12:59 PM

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